Fifteen radical Islamists have been arrested in Moscow with bombs, hand grenades and guns seized, Russian police say.
They say the group were members of an Islamist group called At-Takfir Wal-Hijra.
Police say the arrests were made during early-morning raids at flats in the east of the Russian capital.
Officials said three homemade bombs, detonators and fuses for making more devices were also found.
At-Takfir Wal-Hijra was banned by Russia's Supreme Court in 2010 for "inciting interethnic and interreligious enmity", Russia's Interfax news agency reports.
The group has been mentioned in local media reports several times in the recent years as being one of the most active extremist groups in the region.
It shares its name with a militant group founded in Egypt in the 1960s, although it is not clear whether the organisations are linked.
With just over two months to go before Russia hosts the Winter Olympics in the Black Sea resort of Sochi, these arrests will attract more international attention than usual, says the BBC's Daniel Sandford in Moscow.
In recent years the conflict between Russian forces and separatists in Chechnya has fuelled attacks by Islamists.
The violence has spread across the North Caucasus, including to mainly-Muslim Ingushetia and Dagestan, killing hundreds of people, among them members of the government and security services.
The number of militant attacks in Moscow itself has dropped since the end of Russia's second war in Chechnya, our correspondent reports.
However, the attacks that have taken place have been very serious, such as the suicide bombing at Domodedovo international airport, which killed 37 people in January 2011, he adds.